1. Field of the Invention
This invention relates to a differentially responsive sole of the type with chambers to be filled with material to provide for individual out of normal weight distribution among weight bearing pressure points.
2. Description of the Prior Art
With the increase in running and walking marathons where competition is high, there has been considerable interest in improving footwear, and in tailoring it to an individual's particular weight bearing abnormalities. Many cushions and other devices have been proposed as described in the following U.S. patents to Wolstenholme et al., No. 3,892,077, Zente, No. 3,922,801, Turner et al., No. 4,364,188, Batra, No. 4,398,357, Meyers, No. 4,445,283, and Oatman, No. 4,658,515. While some of these structures provide a degree of cushioning for the user's feet, none of them provide for adequate compensation that is designed to satisfy the needs of an individual's particular foot weight bearing problems, and to accommodate or correct these problems using reproducible data.
During the past decade developments in sensory devices have provided researchers with new diagnostic information about the way people use their feet during ambulation. Some of this information can be used to illustrate how a person distributes, percentages of his or her body weight among selected Biomechanical Weight Bearing Pressure Points (B.W.B.P.P.) of the feet during ambulation. A normal distribution amongst the B.W.B.P.P) has been determined, and minor variations from these norms have been known to cause discomfort and problems both muscular and orthopedic. The resultant problems can occur in the foot, the leg, and even in the hips and lower spine.
The sole of the invention cushions the foot at selected locations where a person is overloading a point and stiffens where a person is underloading a point, the sole therefore providing for customizing to an individual's weight distribution pattern.